Regulation of fermentative metabolism in tomato fruit under low oxygen stress

Abstract

SummaryTomato fruit was stored under a continuous flow of 0% and 3% O2 (balance N2) or air for 7 d at 20°C to study the regulation of fermentative metabolism. The concentrations of ethanol and acetaldehyde were very low during storage at 3% O2 and air. At 0% O2, ethanol and to a lesser extent acetaldehyde, rapidly accumulated in the tissue. However, lactate concentration did not change during the experiment and was not significantly influenced by O2 concentration. Pyruvate decarboxylase (PDC) activity greatly increased in fruit exposed to 3% O2, while activity in fruit exposed to 0% O2 was the same level as the control. Alcohol dehydrogenase (ADH) activity greatly increased in fruit exposed to 3%, but at 0% O2 was the same level as the control. Lactate dehydrogenase (LDH) activity greatly increased in fruit exposed to 3%, but at 0% O2 was the same level as the control. The ADH activity in tomato fruit was about ten times greater than that of PDC activity and about 100 times greater than that of LDH activity during storage. Concentration of NADH in fruit exposed to 3% O2 was greater than that in fruit exposed to 0% O2 and air. Concentrations of pyruvate did not change during storage at 1% O2 and air. At 0% O2, pyruvate rapidly accumulated in its tissue. The K m of ADH in tomato fruit was 0.28 mM for acetaldehyde, and 0.058 mM for NADH. The Km of PDC in tomato fruit was 0.38 mM for pyruvate. The Km of LDH in tomato fruit was 0.18 mM for pyruvate. Possible regulation of fermentative metabolism is briefly considered.